Theoretical Study on Photooxygenation of Large Polycyclic Aromatic Hydrocarbons by Semiempirical Molecular Orbital Methods

Abstract

The photooxygenation reaction of large polycyclic aromatic hydrocarbons (PAHs) composed of more than six benzene rings was investigated by using the semiempirical molecular orbital method. The optimization of the PAHs and their endo-peroxides revealed that oxygen attaches to a pair of carbon atoms which have the largest n-electron density of the highest occupied molecular orbital. The structure of the endo-peroxide of tetrabenzo [de, hi, op,st]pentacene, determined experimentally, could be reproduced by the calculation. The heats of formation for the PAHs, endo-peroxides, and transition states were also calculated, and an energy correlation diagram of the reaction was obtained. The experimental results for the rate of photooxygenation were explained in terms of the energy difference between the initial and transition states in the profile.

Selective access to either a doubly boron-doped tetrabenzopentacene or an oxadiborepin from the same precursor

“…It has been suggested that this deformation governs the reactivity of TBPA toward the electrophilic O 2 molecule, 54 which, under daylight, forms an endo -peroxide connecting the bow/stern C atoms. 37 The B 2 C 4 core of the boron isoster B 2 -TBPA also adopts a boat conformation, such that it should similarly be possible to bridge the B atoms at the bow/stern by a diatomic unit (flip angle = 17.1°). Given that B 2 -TBPA is isoelectronic with the TBPA 2+ dication, suitable reaction partners would be ditopic Lewis bases, rather than electrophiles ( cf.…”

“… 31 – 33 Furthermore, TBPA has a low ionization potential 34 , 35 and the two C atoms located at the cusps of both cove regions 36 accumulate the largest HOMO electron density. 37 B-Doping at these positions, as in the case of B 2 -TBPA , is therefore expected to have a profound influence on the optoelectronic properties of the molecule. Apart from being a pentacene derivative, B 2 -TBPA can be viewed as consisting of two diboraperylenes sharing the central B 2 C 4 ring ( Chart 2 ).…”

On the photo-stability of single molecules. Dibenzoterrylene in 2,3-dimethylnaphthalene crystals

“…In this context it may be surprising that oxygen molecules, having once entered into a 2,3-DMN crystal, can remain there for days in an oxygen free atmosphere inside a cryostat. In general, the mechanism of photo-oxidation is assumed to be sequence of the following processes [17]:…”

Rubrene endoperoxide acetone monosolvate

“…For background to photooxygenation of polycyclic aromatic hydrocarbons, see: Sakai et al (1995). Table 1 Hydrogen-bond geometry (Å , ).…”